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Winter Weather Forecast Discussion
 
(Caution: Version displayed is not the latest version. - Issued 1942Z Apr 30, 2018)
 
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Abbreviations and acronyms used in this product
 
Geographic Boundaries -  Map 1: Color  Black/White       Map 2: Color  Black/White


PROBABILISTIC HEAVY SNOW AND ICING DISCUSSION
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
342 PM EDT MON APR 30 2018

VALID 00Z TUE MAY 01 2018 - 00Z FRI MAY 04 2018

...MOUNTAIN RANGES OF COLORADO...UTAH AND WYOMING...

A CLOSED UPPER LEVEL LOW OVER THE INTERMOUNTAIN WEST WAS IN THE
PROCESS OF OPENING INTO A TROUGH WITH SEVERAL +PV ANOMALIES
CONTINUING TO ROTATE ACROSS THE REGION. ONE PROMINENT PV ANOMALY
WAS LIFTING NORTHEAST FROM UTAH INTO WYOMING...AND IS PROVIDING
THE FOCUS FOR SOME HEAVY PRECIPITATION THAT WILL CONTINUE INTO THE
DAY 1 FORECAST PERIOD (TONIGHT AND TUESDAY). SOME LIGHTNING WAS
EVEN NOTED IN PARTS OF SOUTHWEST WYOMING THIS AFTERNOON JUST AHEAD
OF THE PV ANOMALY...AND WITH SOME CONVECTIVE PRECIP THE LOCALIZED
RATES COULD BE RELATIVELY HIGH. SNOW APPEARS LIKELY AT HIGHER
ELEVATIONS IN WYOMING THROUGH TONIGHT...BUT SHOULD BEGIN TAPERING
OFF DURING THE DAY ON TUESDAY.

PRECIPITATION IN THE WEST ON DAYS 2 AND 3 (TUESDAY NIGHT THROUGH
THURSDAY) WILL BE THE RESULT OF ANOTHER SHORTWAVE...SHARPLY
DIGGING INTO THE WEST COAST OVER THE NEXT 24 HOURS AND REINFORCING
THE LARGE SCALE TROUGH OVER THE WEST. ASSOCIATED DCVA AND
FAVORABLY ALIGNED LEFT EXIT REGION OF AN UPPER LEVEL JET STREAK
SHOULD FOCUS THE HEAVIEST PRECIPITATION FROM UTAH INTO SOUTHWEST
COLORADO ON DAY 2...AND THEN INTO NORTHERN AND EASTERN COLORADO ON
DAY 3.

THROUGH MUCH OF THE PERIOD...SNOW LEVELS APPEAR TO BE AT LEAST
7000-8000 FEET IN MOST LOCATIONS (EXCEPT PERHAPS WYOMING WHERE
THEY COULD BE A LITTLE LOWER). THIS SHOULD RESTRICT HEAVY SNOW TO
THE HIGHEST ELEVATION OF COLORADO...UTAH AND WYOMING. WPC WWD 50
PERCENT OR GREATER PROBABILITIES OF AT LEAST 8 INCHES OF SNOW BY
THURSDAY ARE ALMOST EXCLUSIVELY RESTRICTED TO ELEVATION OF 8000
FEET OR HIGHER IN THIS REGION.

THE MOST FAVORABLE ALIGNMENT OF SYNOPTIC FEATURES AND SUFFICIENTLY
HIGH TERRAIN APPEARS TO BE IN PORTIONS OF NORTHEAST COLORADO FROM
WEDNESDAY EVENING INTO THURSDAY MORNING...PARTICULARLY IN THE
MEDICINE BOW MOUNTAINS AND INTO THE VICINITY OF ROCKY MOUNTAIN
NATIONAL PARK. AS THE PV ANOMALY KICKS THROUGH THE DESERT
SOUTHWEST AND BEGINS TO EJECT TOWARD THE CENTRAL HIGH PLAINS...A
LOW-LEVEL CYCLONE SHOULD DEVELOP NEAR THE CO-KS BORDER WITH A
MID-LEVEL DEFORMATION ZONE FOCUSING TO THE NORTHWEST IN PART OF NE
CO. ADDITIONALLY...THE LEFT EXIT REGION OF AN UPPER LEVEL JET
STREAK (AND ENHANCED UPPER LEVEL DIVERGENCE) WILL BE SITUATED OVER
NE CO AS WELL. THE 12-18 HOUR PERSISTENCE OF STRONG SUPPORT FOR
VERTICAL MOTION SHOULD LEAD TO A PERIOD OF HEAVY SNOW IN THE
AFOREMENTIONED AREAS. IT IS THESE RANGES IN NE CO WHERE WPC WWD
PROBABILITIES OF 18+ INCHES OF SNOW ARE IN EXCESS OF 50 PERCENT.


THE PROBABILITY OF ICING GREATER THAN 0.25 INCHES IS LESS THAN 10
PERCENT FOR DAY 1 THROUGH 3.

LAMERS